Dehydrogenation of dehydrogenatable hydrocarbons

Abstract

A process for the catalytic dehydrogenation of a dehydrogenatable C 2 -plus feed hydrocarbon which comprises the steps of: (a) passing a feed stream comprising the C 2 -plus feed hydrocarbon into a dehydrogenation zone and through at least one bed of dehydrogenation catalyst maintained at dehydrogenation conditions and producing a dehydrogenation zone effluent stream comprising hydrogen, the C 2 -plus feed hydrocarbon and a C 2 -plus product hydrocarbon; (b) forming an oxidation catalyst bed feed stream by admixing an oxygen-containing stream with the dehydrogenation zone effluent stream; (c) passing the oxidation catalyst bed feed stream through a bed of hydrogen selective oxidation catalyst maintained at selective oxidation conditions and producing an oxidation zone effluent stream having a reduced concentration of hydrogen; and (d) recovering the product hydrocarbon from the oxidation zone effluent stream without contacting the oxidation zone effluent stream with dehydrogenation catalyst.

We claim as our invention: 
     
       1. A process for the catalytic dehydrogenation of a dehydrogenatable C 2  -plus feed hydrocarbon which comprises the steps of: (a) passing a feed stream comprising said C 2  -plus feed hydrocarbon into a dehydrogenation zone and through at least one bed of dehydrogenation catalyst maintained at dehydrogenation conditions and producing a dehydrogenation zone effluent stream comprising hydrogen, the C 2  -plus feed hydrocarbon and a C 2  -plus product hydrocarbon;   (b) forming an oxidation catalyst bed feed stream by admixing an oxygen-containing stream with said dehydrogenation zone effluent stream;   (c) passing the oxidation catalyst bed feed stream through a bed of hydrogen selective oxidation catalyst maintained at selective oxidation conditions and producing an oxidation zone effluent stream having a reduced concentration of hydrogen; and   (d) recovering the product hydrocarbon from said oxidation zone effluent stream without contacting said oxidation zone effluent stream with dehydrogenation catalyst.   
     
     
       2. The process of claim 1 wherein said feed hydrocarbon comprises alkylaromatic hydrocarbons. 
     
     
       3. The process of claim 2 wherein said alkylaromatic hydrocarbons are the group consisting of ethylbenzene, diethylbenzene, ethyl toluene, propyl benzene and isopropyl benzene. 
     
     
       4. The process of claim 1 wherein said feed hydrocarbon comprises C 2  -C 16  paraffins. 
     
     
       5. The process of claim 4 wherein said C 2  -C 16  paraffins are selected from the group consisting of propane, butane, hexane and nonane. 
     
     
       6. The process of claim 1 wherein said dehydrogenation catalyst comprises a platinum group component, a tin component, an alkali metal component and a porous inorganic carrier material. 
     
     
       7. The process of claim 1 wherein said dehydrogenation catalyst comprises ferric oxide and chromia. 
     
     
       8. The process of claim 1 wherein said dehydrogenation conditions include a temperature from about 550° C. to about 800° C., a pressure from about 0.3 to about 20 atmospheres absolute and a liquid hourly space velocity from about 0.5 to about 20 hr -1 . 
     
     
       9. The process of claim 1 wherein said hydrogen selective oxidation catalyst comprises a Group VIII noble metal and a metal or metal cation which possesses a crystal ionic radius greater than 1.3 A. 
     
     
       10. The process of claim 1 wherein said hydrogen selective oxidation catalyst comprises platinum, lithium and alumina. 
     
     
       11. The process of claim 1 wherein said selective oxidation conditions include a temperature from about 500° C. to about 800° C., a pressure from about 0.3 to about 20 atmospheres absolute and a liquid hourly space velocity from about 1 to about 20 hr -1 . 
     
     
       12. The process of claim 1 wherein said oxygen-containing stream contains less than 5 mole percent of nitrogen. 
     
     
       13. A process for the catalytic dehydrogenation of a dehydrogenatable C 2  -plus feed hydrocarbon which comprises the steps of: (a) passing a feed stream comprising said C 2  -plus feed hydrocarbon into a dehydrogenation zone and through at least one bed of dehydrogenation catalyst maintained at dehydrogenation conditions and producing a dehydrogenation zone effluent stream comprising hydrogen, the C 2  -plus feed hydrocarbon and a C 2  -plus product hydrocarbon;   (b) forming an oxidation catalyst bed feed stream by admixing an oxygen-containing stream with said dehydrogenation zone effluent stream;   (c) passing the oxidation catalyst bed feed stream through a bed of hydrogen selective oxidation catalyst maintained at selective oxidation conditions and producing an oxidation zone effluent stream having a reduced concentration of hydrogen;   (d) heat exchanging said oxidation zone effluent stream with said feed stream in step (a) to raise the temperature of said feed stream and to lower the temperature of said oxidation zone effluent stream; and   (e) recovering the product hydrocarbon from said oxidation zone effluent stream from step (d) without contacting the oxidation zone effluent stream with dehydrogenation catalyst.   
     
     
       14. The process of claim 13 wherein said feed hydrocarbon comprises alkylaromatic hydrocarbons. 
     
     
       15. The process of claim 14 wherein said alkylaromatic hydrocarbons are selected from the group consisting of ethylbenzene, diethylbenzene, ethyl toluene, propyl benzene and isopropyl benzene. 
     
     
       16. The process of claim 13 wherein said feed hydrocarbon comprises C 2  -C 16  paraffins. 
     
     
       17. The process of claim 15 wherein said C 2  -C 16  paraffins are selected from the group consisting of propane, butane, hexane and nonane. 
     
     
       18. The process of claim 13 wherein said dehydrogenation catalyst comprises a platinum group component, a tin component, an alkali metal component and a porous inorganic carrier material. 
     
     
       19. The process of claim 13 wherein said dehydrogenation catalyst comprises ferric oxide and chromia. 
     
     
       20. The process of claim 13 wherein said dehydrogenation conditions include a temperature from about 550° C. to about 800° C., a pressure from about 0.3 to about 20 atmospheres absolute and a liquid hourly space velocity from about 0.5 to about 20 hr -1 . 
     
     
       21. The process of claim 13 wherein said hydrogen selective oxidation catalyst comprises a Group VIII noble metal and a metal or metal cation which possesses a crystal ionic radius greater than 1.3 A. 
     
     
       22. The process of claim 13 wherein said hydrogen selective oxidation catalyst comprises platinum, lithium and alumina. 
     
     
       23. The process of claim 13 wherein said selective oxidation conditions include a temperature from about 500° C. to about 800° C., a pressure from about 0.3 to about 20 atmospheres absolute and a liquid hourly space velocity from about 1 to about 20 hr -1 . 
     
     
       24. The process of claim 13 wherein said oxygen-containing stream contains less than 5 mole percent of nitrogen.